1. Field of the Invention
The present invention relates to a musical instrument for electrically generating a musical tone through an electro-acoustic transducer like an electrical or electronic musical instrument and, more particularly, to a musical instrument with a compact electro-acoustic transducer and capable of generating a heavy bass sound and a musical instrument capable of generating a musical tone with good sound quality over the entire tone generation range, in particular, in a bass range.
2. Description of the Prior Art
Conventionally, electronic and electrical musical instruments are known as musical instruments comprising an electro-acoustic transducer (to be referred to as an acoustic apparatus hereinafter).
An electrical musical instrument comprises a tone generating device which can directly generate a tone by a mechanical or acoustic vibration similar to a guitar, drum, wind instrument, or the like. The instrument temporarily converts the mechanical vibration or tone into an electrical signal and electrically amplifies the electrical signal. The instrument re-converts the amplified electrical signal into an acoustic wave using an acoustic apparatus to produce a corresponding sound. Thus, the instrument can generate an acoustic wave in a larger tone volume than that when it is directly generated, or can produce a tone with a special effect.
On the other hand, an electronic musical instrument electrically forms a musical tone signal using an electronic circuit with an oscillator, a memory, and the like in accordance with an instruction from a tone generation instruction means such as a keyboard, drum pad, breath input device, or the like, and produces a sound corresponding to the musical tone signal using an acoustic apparatus.
The electrical/electronic musical instrument is generally equipped with a separate speaker box as a speaker system for the acoustic apparatus. In this case, the speaker box causes an increase in cost or becomes a design limitation factor.
In some instruments, a pedal box serves as a speaker box, and the speaker system is housed in the pedal box. In this case, however, both a box volume and a speaker diameter are reduced, and a bass sound cannot be satisfactorily reproduced.
In the electrical/electronic musical instrument, the frequency characteristic of the acoustic apparatus is fixed. Thus, good sound quality cannot always be obtained over the entire tone range for an electronic keyboard instrument having a wide tone generation range.
As the electrical/electronic musical instrument, a portable musical instrument which incorporates an acoustic apparatus, is easily carried, and has a shape and size suitable for a hand-held performance is also known.
The portable musical instrument is required to have a compact main body in terms of easy carrying and easy standing performance, and a small-diameter speaker is disposed in the compact main body. For this reason, the conventional portable musical instrument cannot satisfactorily reproduce a bass sound and can only produce a poor sound. Some portable musical instruments include a resonator for producing a bass sound. However, the musical instrument of this type has a large main body like an acoustic guitar to obtain sufficient sound quality, and is not suitable for a standing performance. If the instrument of this type has a size suitable for a standing performance, sufficient sound quality cannot be obtained.